1. Field of the Invention
This invention relates to apparatus for tensioning and advancing material, such as textile material. More particularly, this invention relates to tensioning and advancing material while dynamically maintaining alignment of the material.
2. Technical Considerations and Prior Art
In the manufacture of textiles, it is a frequent practice to knit strands of yarn into tubular configurations generally referred to as yarn socks so that the strands of yarn may be conveniently processed while in a readily deknitted, bulk form.
In processing yarn which will eventually be woven into carpets, knitting yarn into yarn socks is generally a standard practice prior to dyeing the yarn.
In the past, numerous difficulties have been encountered in knitting strands of yarn into these socks. Generally, these difficulties involve numerous broken needles in the knitting machines and lack of uniformity in the coarse of the knit produced by different knitting machines.
It has been found by the inventors of the present invention that these problems are, by and large, created downstream of the knitting machine by the apparatus which tensions and advances the socks as they emerge from the knitting machine. The prior art tensioning apparatus generally utilizes a pair of rollers between which the socks are passed. The rollers are both positively driven and are biased together by a pair of springs acting on opposite ends of one of the rollers. A major problem with this type of roller is that it is difficult to distribute the force from which the rollers engage the socks equally over the surfaces of the socks. This is because it is necessary to coordinate the tension on the two springs by advancing and retracting adjustment screws which compress the springs. The adjustment to the springs also effects the stitch density of the socks knitted by the heads. Due to the fact that there are two springs with each set of rollers, this becomes a tedious and difficult task, often resulting in knitting heads which produce non-uniform socks that, when later woven into textile products such as carpets, produce products of inferior quality.
It has been found that the positive drive utilized with this prior art system causes needles in the knitting heads to frequently break because the positive drives apply tension to the socks, which increases dramatically when the yarn for some reason becomes hung up on one or more needles. This tension can then, of course, be transferred to other needles, resulting in additional needle breakage. When the needles in the knitting machines break, the knitting machines must be stopped and the needles replaced so that the stitch of the socks will be uniform and will not be afflicted with runs or other anomalies. Furthermore, the machines must be stopped to remove the broken needles so that the needles do not become entangled in the various mechanisms associated with the knitting machines.